4=-4.9x^2+26x

Solution for 4=-4.9x^2+26x equation:

4=-4.9x^2+26x

We move all terms to the left:

4-(-4.9x^2+26x)=0

We get rid of parentheses

4.9x^2-26x+4=0

a = 4.9; b = -26; c = +4;
Δ = b2-4ac
Δ = -262-4·4.9·4
Δ = 597.6
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-26)-\sqrt{597.6}}{2*4.9}=\frac{26-\sqrt{597.6}}{9.8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-26)+\sqrt{597.6}}{2*4.9}=\frac{26+\sqrt{597.6}}{9.8}
$